My German immigrant ancestor and his brother settled in Adams County, Illinois, in the 1850s. His mother and her second husband also immigrated to the United States, settling some ninety-eight miles away. Early in my research, because I didn’t find her near my ancestor and his brother, I assumed that she never immigrated because “people settled together.”
But there were a few other factors at work in this family. The “boys” were adults when they immigrated and they actually did settle in an area where a few of their former German neighbors (and perhaps an errant relative I simply haven’t tracked down yet) settled. Their mother had a second husband she married in Germany and it’s possible that he had connections in the area where the mother settled.
There area always factors at work. Sometimes we just don’t know what they are.